US2359302A - Incandescent lamp and method of manufacture - Google Patents

Description

Oct. 3, 1944. I L.-W. CURTIS 2,359,302

INCANDESCENT LAMP AND METHOD OF MANUFACTURE Filed June 11, 1942 INVENTOR [am/v W CuRT/s BY am 1 M Y 7 ATTORNEYS Patented Oct. 3, 1944 INCANDESCENT LAMP AND METHOD OF MANUFACTURE Lorin w. own, Verona, N. 1., alslnor to rung- Sol Lamp Works Inc., Newark, N. J., a corporae tion of Delaware Application June 11, 1942, Serial No. 44s,ss4

6 Claims. (01. 115-40) This invention relates to incandescent lamps and particularly lamps of the miniature type.

The invention relates to the mounting and the welding of the legs of the coiled filaments of miniature incandescent lamps to the filament support wires and more particularly to the provision of reinforced welds therefor. One object of the invention is a novel and improved method of forming coiled'filaments for miniature incandescent lamps with reinforced legs for facilitating the mounting of the filaments upon the wire supports.

Further objects of the invention will hereinafter appear.

For a better understanding of the invention reference may be had to the accompanying drawmount of the incandescent lamp embodying the invention, the glass envelope or bulb and the base being omitted for convenience in illustration. This mountincludes a'glass press I and a pair of filament support wires 2 having'mounted thereon a coiled-coil filament 3, the latter being formed of a continuous coil of fine filamentary wire such as tungsten coiled'about itself into larger Lcoils with legs 4 welded at the points 5 to the support wires 2. The legs 4 comprise cores 6 within the primarycoil for reinforcing them for the welding formed at the points 5. By providing the legs 4 with the reinforcing cores 6 the legs 4 of the filament may be firmly and permanently welded to the mount wires 2 with facility.

The coiled-coil filament 3 is formed and prepared for the mounting operation by first forming the filament with the primary mandrel therein and then dissolving out the intermediate portion of the primary mandrel to leave the leg filament portions of the mandrel in the coil as a reinforcement for mounting and welding the filament. By thus providing for the utilization of portions of the primary mandrel about which the wire is closely wound as a reinforcing means for the mount and weld, the mount meets the require ments as to endurance and ruggedness of con struction for heavy duty service, such for example as used on tanks and the like. This method alse eliminates the conventional and tedious step in the preparation of the filament for the mount of making inserts of smaller diameter into the filament legs which was usually accompanied with theproblem of retaining the more or less loosely mounted inserts in proper place during the welding operation.

Th method of forming and preparing the coiled-coil filament for mounting is illustrated in Figs". 1 to 5, inclusive. Fig. 1 illustrates the forming of the coiled filament about the primary mandrel 6', this mandrel being of any suitable metal, as for example brass, iron or molybdenum, and Fig. 2 illustrates the filament after the coiling of the filament into the larger coil with the primary mandrel 6 therein. After the filament is thus formed, the filament legs 4 are then coated with some substance which is neutral to the acid conventionally used for dissolving the mandrel i cut of the coil. I have found suitable for this purpose a high melting temperature wax contained in a conventionally illustrated container 1 into which the legs 4 of the filament are dipped by hand or otherwise. I have obtained good results with the use of carnauba wax, but any wax with a high melting point could be utilized, that is a melting point above the temperature of the acid bath. It is melted and maintained in a liquid state in a shallow dish or container 1 which is heated in any suitable manner, as for example by a hot plate, omitted from the drawing for convenience in illustration. The filament legs 4 thus dipped in the coating wax or other coating material 8 is illustrated in Fig. 4, which illustrates a coating of material 8 on these legs. With the filament legs thus coated, as shown in Fig. 4, the

filament is immersed in an acid bath for the purpose of dissolving out the mandrel 6' from the coiled-coil part of the filament so as to leave only the cores 6 in the end or leg portions. Fig. 4 shows the filament after the dissolution of mandrel 6' has taken place. The acid bath used for this purpose depends upon the character of the mandrel. With a mandrel of brass a conventional bath is one of nitric acid. With" a mandrel of iron,

a bath of hydrochloric acid is conventional and for molybdenum a bath of nitric and sulphuric acids mixed may be employed. In dissolving the mandrel, it is essential to keep the solution cooled below the inciting point of the wax, since there is a considerable amount of heat generated from the reaction of the mandrel with the acid. This may-bejd'one in a bath of cold water. If too many coils are placed in the acid at one time, there may be a sumcient amount of heat arising from the reaction to melt oil the wax coating 8 of Fig. 4 and allow the acid to attack the mandrel part or cores 6 within the leg sections and, accordingly,

filament in an acid 'mary mandrel portion intermediate the legs and a relatively small quantity of filaments are treated at one time when dissolving the primary mandrel 6 out of the filament. With the coiledcoil filament thus obtained, as shown in Fig. 4, the next step is the removal of the wax or neutral coating 8 from the legs 4 of the filament. Th1! may be eflected with a hot caustic or with a suitable wax solvent; as ior example ethylen di- Fig. 5 and in this form it is now ready to situated by welding the iegs 4 to t e mount, sum port wires 2 with me c res 5 in the legs which formed part of the original primary mandrel chloride. The filament fOlllld is shown army and snugly held and reta ned time eieseiy wound coils of the legs or ma icure g The filament, mai be subieet to e ventio nai treatiiiiitswitli a caustic oath and rinsing in flat ath to disso v out the iS-ri':

to leave the coated leg mandrel portions as reiniorcing cores for the legs, removing the neutral coatings from the legs, and then welding the mandrel supported legs of the filament to filament support wires.

2. The method of forming and mounting I coiled-coil filament in an incandescent lamp which consists in forming a coiled-coil filament with straight leg or end portions havihg a primary mandrel extending throughout the smaller filament coil, coating the leg portions of the filament with a neutral substance which melts at I high temperature, immersing the filament in an acid bath to dissolve out the primary mandrel portion intermediate the legs and to leave the coated leg mandrel portions as reinforcing cores for the legs, dissolving the neutral coatings from the legs, and then welding the mandrel supported legs of the filament to filament support wires.

3. The method forming and mounting a coiled-coil filament inan incandescent lamp which consists in forming 'a coiled-coil filament with straight leg or end portions having a pri- Fill mar mandrel extending throughout the smaller aasasoa filament coil, coatinfl the leg portions of the filament with wax, immersing the filaments in an acid bath to dissolve out the primary mandrel portion intermediate the legs and to leave the coated leg mandrel portions as reiniorcing'cores lot the legs, dissolving the wax coatings from the legs; and then welding the mandre supported legs or the filament to lament support wires.

1. The method of tanning and mounting a coiled-coil e ement in an incandescen imp tiniest cdiisistfi iii taming a eaued -eau filament with straight leg or eiiujxsr'uans having a priiiiary mandrel extending thro ighojit the filament, coating the leg portions of the filament with a neutral substan e, the elements in' a acid bath to dissolve out the primary man rel screenwriter-mediate the legs sea to leave the ea dill3m ta' s i ipr inz ti t th legs, maintaining tlie'acid bath at a temperature during the di i ti n ma b gw he tan e, removingthe hiitral nits nan the malaria sii f lidited legs a: the filament t5 filament wires. 1 I I 'I e 'ifit i 6 aml 6 ime tureinsans c nt ambsa iith ips l v. oi 1017mm" a coiled ,illafiient witli ls'traight e; o an t on e? 1 1i -l i l m n ala throughout'the filam t and oifja difi'erent in t'al o t a of w h th m l emsn i term ai in: the leg portiog oftige iiiar'rient ,a net tral intimate i8 ilrzit'ttmg nit Elmira 38? tie against acid attack, wholly immersing the filament in an acid bath to dissolve out the mandrel portion intermediate the legs and to leave the coated leg portions of the mandrel as reinforcing cores for the legs and removing the neutral coat.- ings from the legs preparatory to mounting the filament thus formed by fastening the reinforced straight leg portions to filament supportwirea.

0. The method 01 iorming and mounting a toiled-coil filament in an incandescent lamp which consists in forming a coiled-coil filament with straight smaller coil portions having a primm mandrel'ex'tendin'g throughout the smaller coil, coating the straight portions of the coiledcoil filament with a neutral substance, immersing the filament in an acid bath to dissolve out the mandrel portion intermediate the straight por-' tions and to leave the coated straight mandrel portions as reinforcing cores therefor, removing the neutral coating from the straight portions, and then fastening the mandrel supported straight portions oi the coiled-coil filament to filament support wires.

LORIN W.- CURTIS.

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